I have to develop on a gallery-like component modx gallery modx but I do not have to upload pictures but the youtube url and the image will be the thumb youtube obtained as follows:
http://img.youtube.com/vi/ <insert-youtube-video-id-here> / mqdefault.jpg
I had decided to solve using the gallery modx in the url field and putting the link to the video. But anyway my client must submit a picture, I wish this was not mandatory but was taken into the automatic thumb from youtube or do not have displayed nothing in the backend.
This is GalleryrowTpl of my Gallery:
<li>
<a href="[[+url]]" rel="prettyPhoto[vv_gal]" class="prettyGalleryThumb"><img src="http://img.youtube.com/vi/[[!grab_youtube_video_id? &url=`[[+url]]`]]/mqdefault.jpg" alt="[[+name]]" /></a>
<h3>[[+name]]</h3>
<p>[[+description]]</p>
</li>
